An osteopontin-integrin interaction plays a critical role in directing adipogenesis and osteogenesis by mesenchymal stem cells

The biological function of integrin-linked kinase on bone formation

Bone remodeling process is the basis for maintaining normal bone microstructure and promoting fracture repair. Recent studies have proven that integrins can promote bone formation and fracture repair. Integrin-linked kinase (ILK), as the proximal effector of the integrin receptor, is a key protein factor linking integrin and cytoskeleton. It is involved in crucial cellular processes including proliferation, survival, differentiation, migration, invasion, and angiogenesis reflects on systemic changes in the kidney, heart, muscle, skin, and vascular system. At present, the regulation effect of ILK in bone formation attracts the attention of researchers. This review emphasizes that ILK as a key molecule affects the functions of bone marrow stromal cells (BMSCs) and osteoblasts, and regulates bone formation. Additionally, ILK plays a key role in the process of"angiogenic-osteogenic coupling ". The present role of ILK in the pathogenesis of osteoporosis is also described. Strategies that target ILK may as a new prospective treatment for osteoporosis (OP).

Untangling Ariadne's Thread Within the Bone Marrow Maze: A Close-Up View of Stem/Progenitor Cells' Interactome and Secretome

The bone marrow (BM) is a multifactorial, highly dynamic, still not fully "mapped," reservoir. The BM labyrinthine landscape is subject to a relentless debate on the specialized and stem/progenitor cells' scattering within designated microareas. Certainly, BM tissue plays a watchdog role in bone modeling and remodeling, hematopoiesis, immune surveillance, and endocrine response integration. Parameters like tissue topographical distinctiveness, stiffness and porosity grade, and cells' behavioral idiosyncrasies in terms of stem/progenitor cell housing, activation, and motility represent a knotty problem not easily solved. Given that the disruption of BM microdomains has been associated with a number of severe pathological disorders, the comprehension and preservation of the BM workspace at multiple levels have become mandatory. Solid evidence has showed the existence of an intricate and tightly regulated cross-talk between the BM cellular occupants. Direct physical cell-cell connections and soluble mediators, including cytokines, chemokines, growth factors, exosomes and microvesicles, orchestrate composite intracellular signaling routes. The spatiotemporal action of definite biofactors ensures a functional blood-producing organ with a physiological bone turnover and prompts the action of multipotent stromal/hematopoietic cells. Recently, significant research efforts have been addressed to build bioengineered niche-mimic models based on biofunctionalized scaffolds and organoid-like constructs. These artificial BM niches combine and transduce various aspects of bioinformatics and tissue engineering to unravel the complexities of BM organization. This chapter aims to unfold the recent breakthroughs in the understanding of a BM intramural cell-cell dialogue in a physiological and, in some cases, within an inflammatory background. BM maze is gradually being discovered, but there is still a long way to go.

Novel Clinical Insights into the Pathogenesis of Posttraumatic Elbow Stiffness: An Expression Profile Analysis of Contracted Joint Capsule in Human

Background

Posttraumatic elbow stiffness is a complex complication with two characteristics of capsular contracture and heterotopic ossification. Currently, genomic mechanisms and pathogenesis of posttraumatic elbow stiffness remain inadequately understood. This study aims to identify differentially expressed genes (DEGs) and elucidate molecular networks of posttraumatic elbow stiffness, providing novel insights into disease mechanisms at transcriptome level.

Methods

Global transcriptome sequencing was conducted on six capsular samples from individuals with posttraumatic elbow stiffness and three control capsular samples from individuals with elbow fractures. Differentially expressed genes (DEGs), microRNAs, and long non-coding RNAs (LncRNAs) were identified and analyzed. Functional enrichment analysis was performed, and the associated protein-protein interaction (PPI) network was constructed. MicroRNAs targeting these DEGs were identified, and transcription factors (TFs) targeting DEGs were predicted using the ENCODE database. Finally, key DEGs were validated by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

A total of 4909 DEGs associated with protein-coding, LncRNA and microRNA were detected, including 2124 upregulated and 2785 downregulated. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the DEGs were significantly enriched in 36 signaling pathways, notably involving inflammatory responses and extracellular matrix (ECM) receptor interactions. The protein-protein interaction (PPI) network analysis highlighted genes such as SPP1, IBSP, MMP13 and MYO1A as having higher degrees of connectivity. Key microRNAs (hsa-miR-186-5p, hsa-miR-515-5p, and hsa-miR-590-3p) and transcription factors (TFDP1 and STAT3) were predicted to be implicated in the pathogenesis of posttraumatic elbow stiffness through the microRNA-transcription factor regulatory network analysis.

Conclusion

The study provided insights into the molecular mechanisms underlying the changes in the contracted capsules associated with posttraumatic elbow stiffness. Hub genes including SPP1, IBSP, MMP13, and MYO1A, key microRNAs (has-miR-186-5p, has-miR-515-5p, hsa-miR-590-3p) and TFs (TFDP1 and STAT3) may serve as prognostic and therapeutic targets of posttraumatic elbow stiffness, and provide a new idea for the future research direction of clinical treatment.

Polyetheretherketone Double Functionalization with Bioactive Peptides Improves Human Osteoblast Response

In recent years, the demand for orthopedic implants has surged due to increased life expectancy, necessitating the need for materials that better mimic the biomechanical properties of human bone. Traditional metal implants, despite their mechanical superiority and biocompatibility, often face challenges such as mismatched elastic modulus and ion release, leading to complications and implant failures. Polyetheretherketone (PEEK), a semi-crystalline polymer with an aromatic backbone, presents a promising alternative due to its adjustable elastic modulus and compatibility with bone tissue. This study explores the functionalization of sandblasted 3D-printed PEEK disks with the bioactive peptides Aoa-GBMP1α and Aoa-EAK to enhance human osteoblast response. Aoa-GBMP1α reproduces 48-69 trait of Bone Morphogenetic Protein 2 (BMP-2), whereas Aoa-EAK is a self-assembling peptide mimicking extracellular matrix (ECM) fibrous structure. Superficial characterization included X-ray photoelectron spectroscopy (XPS), white light interferometer analysis, static water contact angle (S-WCA), and force spectroscopy (AFM-FS). Biological assays demonstrated a significant increase in human osteoblast (HOB) proliferation, calcium deposition, and expression of osteogenic genes (RUNX2, SPP1, and VTN) on functionalized PEEK compared to non-functionalized controls. The findings suggest that dual peptide-functionalized PEEK holds significant potential for advancing orthopedic implant technology.

Macrophage depletion in inflamed rat knees prevents the activation of synovial mesenchymal stem cells by weakening Nampt and Spp1 signaling

BACKGROUND

Macrophages and mesenchymal stem cells (MSCs) engage in crucial interplay during inflammation and have significant roles in tissue regeneration. Synovial MSCs, as key players in joint regeneration, are known to proliferate together with macrophages in synovitis. However, the crosstalk between synovial MSCs and macrophages remains unclear. In this study, we investigated changes in the activation of synovial MSCs in inflamed rat knees following selective depletion of macrophages with clodronate liposomes.

METHODS

Acute inflammation was induced in rat knee joints by injection of carrageenan (day 0). Clodronate liposomes were administered intra-articularly on days 1 and 4 to deplete macrophages, with empty liposomes as a control. Knee joints were collected on day 7 for evaluation by histology, flow cytometry, and colony-forming assays. Concurrently, synovial MSCs were cultured and subjected to proliferation assays, flow cytometry, and chondrogenesis assessments. We also analyzed their crosstalk using single-cell RNA sequencing (scRNA-seq).

RESULTS

Clodronate liposome treatment significantly reduced CD68-positive macrophage numbers and suppressed synovitis. Immunohistochemistry and flow cytometry showed decreased expression of CD68 (a macrophage marker) and CD44 and CD271 (MSC markers) in the clodronate group, while CD73 expression remained unchanged. The number of colony-forming cells per 1000 nucleated cells and per gram of synovium was significantly lower in the clodronate group than in the control group. Cultured synovial MSCs from both groups showed comparable proliferation, surface antigen expression, and chondrogenic capacity. scRNA-seq identified seven distinct synovial fibroblast (SF) subsets, with a notable decrease in the Mki67+ SF subset, corresponding to synovial MSCs, in the clodronate group. Clodronate treatment downregulated genes related to extracellular matrix organization and anabolic pathways in Mki67+ SF. Cell-cell communication analysis revealed diminished Nampt and Spp1 signaling interaction between macrophages and Mki67+ SF and diminished Ccl7, Spp1, and Csf1 signaling interaction between Mki67+ SF and macrophages in the clodronate group. Spp1 and Nampt promoted the proliferation and/or chondrogenesis of synovial MSCs.

CONCLUSIONS

Macrophage depletion with clodronate liposomes suppressed synovitis and reduced the number and activity of synovial MSCs, highlighting the significance of macrophage-derived Nampt and Spp1 signals in synovial MSC activation. These findings offer potential therapeutic strategies to promote joint tissue regeneration by enhancing beneficial signals between macrophages and synovial MSCs.

Relationship between adipocytes and hematological tumors in the bone marrow microenvironment: a literature review

Background and Objective

The bone marrow microenvironment is closely related to normal hematopoiesis and hematologic tumors. Adipocytes are an important part of the bone marrow microenvironment, in which they can release free fatty acids (FFAs) through lipolysis and secrete adipocytokines, etc., and participate in normal hematopoiesis, which is closely related to the occurrence and treatment of hematological tumors. In this review, we aim to discuss how bone marrow adipocytes (BMAs) can influence the proliferation, apoptosis, and chemotherapy resistance of cancer cells by reprogramming lipid metabolism and the secretion of various adipocytokines.

Methods

Studies from 2000 to July 2024 were reviewed from PubMed, Springer Link, and the Web of Science using the keywords bone marrow microenvironment, adipocytes, lipid metabolism, adipocytokines, hematological tumor, cancer, and their combinations. Unreliable articles such as those that are old and have a low impact factor are excluded, and there is no restriction on language.

Key Content and Findings

Adipocytes can regulate the proliferation and differentiation of hematopoietic stem cells (HSCs) by secreting inflammatory factors and adipocytokines to maintain hematopoietic homeostasis. Adipocytes can also stimulate and accelerate the occurrence and progression of hematological tumors by secreting adipocytokines and mediating the reprogramming of lipid metabolism. Moreover, abundant adipocytes in bone marrow can protect tumor cells by physically blocking and/or secreting cytokines, leading to chemotherapy resistance.

Conclusions

Therefore, the targeted inhibition of related lipid metabolism pathways and adipocytokines might be a potential therapeutic target for hematological tumors, which would be helpful to inhibit tumor growth and correct chemotherapy resistance.

Intracellular osteopontin potentiates the immunosuppressive activity of mesenchymal stromal cells

INTRODUCTION

Mesenchymal stromal cell (MSC)-based cell therapy is a promising approach for various inflammatory disorders based on their immunosuppressive capacity. Osteopontin (OPN) regulates several cellular functions including tissue repair, bone metabolism and immune reaction. However, the biological function of OPN in regulating the immunosuppressive capacity of MSCs remains elusive.

OBJECTIVES

This study aims to highlight the underlying mechanism of the proinflammatory cytokines affect the therapeutic ability of MSCs through OPN.

METHODS

MSCs in response to the proinflammatory cytokines were collected to determine the expression profile of OPN. In vitro T-cell proliferation assays and gene editing were performed to check the role and mechanisms of OPN in regulating the immunosuppressive capacity of MSCs. Inflammatory disease mouse models were established to evaluate the effect of OPN on improving MSC-based immunotherapy.

RESULTS

We observed that OPN, including its two isoforms iOPN and sOPN, was downregulated in MSCs upon proinflammatory cytokine stimulation. Interestingly, iOPN, but not sOPN, greatly enhanced the immunosuppressive activity of MSCs on T-cell proliferation and thus alleviated the inflammatory pathologies of hepatitis and colitis. Mechanistically, iOPN interacted with STAT1 and mediated its deubiquitination, thereby inducing the master immunosuppressive mediator inducible nitric oxide synthase (iNOS) in MSCs. In addition, iOPN expression was directly downregulated by activated STAT1, which formed a negative feedback loop to restrain MSC immunosuppressive capacity.

CONCLUSION

Our findings demonstrated that iOPN expression modulation in MSCs is a novel strategy to improve MSC-based immunotherapy.

NIR-Triggered Release of Nitric Oxide by Upconversion-Based Nanoplatforms to Enhance Osteogenic Differentiation of Mesenchymal Stem Cells for Osteoporosis Therapy

Stem cell therapy is an attractive approach to bone tissue regeneration in osteoporosis (OP); however, poor cell engraftment and survival within injured tissues limits its success in clinical settings. Nitric oxide (NO) is an important signaling molecule involved in various physiological processes, with emerging evidence supporting its diverse roles in modulating stem cell behavior, including survival, migration, and osteogenic differentiation. To control and enhance osteogenic differentiation of mesenchymal stem cells (MSCs) for OP therapy, we designed a near-infrared (NIR) light-triggered NO-releasing nanoplatform based on upconversion nanoparticles (UCNPs) that converts 808-nm NIR light into visible light, stimulating NO release by light control. We demonstrate that the UCNP nanoplatforms can encapsulate a light-sensitive NO precursor, Roussin's black salt (RBS), through the implementation of a surface mesoporous silica coating. Upon exposure to 808-nm irradiation, NO is triggered by the controlled upconversion of UCNP visible light at the desired time and location. This controlled release mechanism facilitates photoregulated differentiation of MSCs toward osteogenic lineage and avoids thermal effects and phototoxicity on cells, thus offering potential therapeutic applications for treating OP in vivo. Following the induction of osteogenic differentiation, the UCNP nanoplatforms exhibit the capability to serve as nanoprobes for the real-time detection of differentiation through enzymatic digestion and fluorescence recovery of UCNPs, enabling assessment of the therapeutic efficacy of OP treatment. Consequently, these UCNP-based nanoplatforms present a novel approach to control and enhance osteogenic differentiation of MSCs for OP therapy, simultaneously detecting osteogenic differentiation for evaluating treatment effectiveness.

Advancing bone regeneration: Unveiling the potential of 3D cell models in the evaluation of bone regenerative materials

Bone, a rigid yet regenerative tissue, has garnered extensive attention for its impressive healing abilities. Despite advancements in understanding bone repair and creating treatments for bone injuries, handling nonunions and large defects remains a major challenge in orthopedics. The rise of bone regenerative materials is transforming the approach to bone repair, offering innovative solutions for nonunions and significant defects, and thus reshaping orthopedic care. Evaluating these materials effectively is key to advancing bone tissue regeneration, especially in difficult healing scenarios, making it a critical research area. Traditional evaluation methods, including two-dimensional cell models and animal models, have limitations in predicting accurately. This has led to exploring alternative methods, like 3D cell models, which provide fresh perspectives for assessing bone materials' regenerative potential. This paper discusses various techniques for constructing 3D cell models, their pros and cons, and crucial factors to consider when using these models to evaluate bone regenerative materials. We also highlight the significance of 3D cell models in the in vitro assessments of these materials, discuss their current drawbacks and limitations, and suggest future research directions. STATEMENT OF SIGNIFICANCE: This work addresses the challenge of evaluating bone regenerative materials (BRMs) crucial for bone tissue engineering. It explores the emerging role of 3D cell models as superior alternatives to traditional methods for assessing these materials. By dissecting the construction, key factors of evaluating, advantages, limitations, and practical considerations of 3D cell models, the paper elucidates their significance in overcoming current evaluation method shortcomings. It highlights how these models offer a more physiologically relevant and ethically preferable platform for the precise assessment of BRMs. This contribution is particularly significant for "Acta Biomaterialia" readership, as it not only synthesizes current knowledge but also propels the discourse forward in the search for advanced solutions in bone tissue engineering and regeneration.

Targeting adipocyte ESRRA promotes osteogenesis and vascular formation in adipocyte-rich bone marrow

Excessive bone marrow adipocytes (BMAds) accumulation often occurs under diverse pathophysiological conditions associated with bone deterioration. Estrogen-related receptor α (ESRRA) is a key regulator responding to metabolic stress. Here, we show that adipocyte-specific ESRRA deficiency preserves osteogenesis and vascular formation in adipocyte-rich bone marrow upon estrogen deficiency or obesity. Mechanistically, adipocyte ESRRA interferes with E2/ESR1 signaling resulting in transcriptional repression of secreted phosphoprotein 1 (Spp1); yet positively modulates leptin expression by binding to its promoter. ESRRA abrogation results in enhanced SPP1 and decreased leptin secretion from both visceral adipocytes and BMAds, concertedly dictating bone marrow stromal stem cell fate commitment and restoring type H vessel formation, constituting a feed-forward loop for bone formation. Pharmacological inhibition of ESRRA protects obese mice against bone loss and high marrow adiposity. Thus, our findings highlight a therapeutic approach via targeting adipocyte ESRRA to preserve bone formation especially in detrimental adipocyte-rich bone milieu.

Chromatin accessibility profiling reveals that human fibroblasts respond to mechanical stimulation in a cell-specific manner

Fibroblasts in the skin are highly heterogeneous, both in vivo and in vitro. One difference between follicular (dermal papilla fibroblasts [DP]) and interfollicular fibroblasts (papillary fibroblasts [PFi]) in vitro is their ability to differentiate in response to osteogenic media (OM), or mechanical stimulation. Here, we asked whether differences in the ability of DP and PFi to respond to differentiation stimuli are due to differences in chromatin accessibility. We performed chromatin accessibility and transcriptional profiling of DP and PFi in human skin, which arise from a common progenitor during development, yet display distinct characteristics in adult tissue and in vitro. We found that cells cultured in growth media had unique chromatin accessibility profiles; however, these profiles control similar functional networks. Upon introduction of a chemical perturbation (OM) to promote differentiation, we observed a divergence not only in the accessible chromatin signatures but also in the functional networks controlled by these signatures. The biggest divergence between DP and PFi was observed when we applied 2 perturbations to cells: growth in OM and mechanical stimulation (a shock wave [OMSW]). DP readily differentiate into bone in OMSW conditions, while PFi lack differentiation capability in vitro. In the DP we found a number of uniquely accessible promoters that controlled osteogenic interaction networks associated with bone and differentiation functions. Using ATAC-seq and RNA-seq we found that the combination of 2 stimuli (OMSW) could result in significant changes in chromatin accessibility associated with osteogenic differentiation, but only within the DP (capable of osteogenic differentiation). De novo motif analysis identified enrichment of motifs bound by the TEA domain (TEAD) family of transcription factors, and inter-cell comparisons (UpSet analysis) displayed large groups of genes to be unique to single cell types and conditions. Our results suggest that these 2 stimuli (OMSW) elicit cell-specific responses by modifying chromatin accessibility of osteogenic-related gene promoters.

Development of hydrogel-based composite scaffolds containing eggshell particles for bone regeneration applications

This study describes the development and characterization of novel composite scaffolds, made of an alginate-chitosan hydrogel matrix containing eggshell (ES) particles, for bone tissue engineering applications. Scaffolds with ES particles, either untreated or treated with phosphoric acid to create a nanotextured particle surface, were compared to scaffolds without particles. Results indicate that the nanotexturing process exposed occluded ES proteins orthologous to those in human bone extracellular matrix. Scaffolds with ES or nanotextured ES (NTES) particles had a higher porosity (81 ± 4% and 89 ± 5%, respectively) than scaffolds without particles (59 ± 5%) (p = .002 and p < .001, respectively). Scaffolds with NTES particles had a larger median pore size (113 μm [interquartile range [IQ]: 88-140 μm]) than scaffolds with ES particles (94 μm [IQ: 75-112 μm]) and scaffolds without particles (99 μm [IQ: 74-135 μm]) (p < .001 and p = .011, respectively). The compressive modulus of the scaffolds with ES or NTES particles remained low (3.69 ± 0.70 and 3.14 ± 0.62 kPa, respectively), but these scaffolds were more resistant to deformation following maximum compression than those without particles. Finally, scaffolds with ES or NTES particles allowed better retention of human mesenchymal stem cells during seeding (53 ± 12% and 57 ± 8%, respectively, vs. 17 ± 5% for scaffolds without particles; p < .001 in both cases), as well as higher cell viability up to 21 days of culture (67 ± 17% and 61 ± 11%, respectively, vs. 15 ± 7% for scaffolds without particles; p < .001 in both cases). In addition, alkaline phosphatase (ALP) activity increased up to 558 ± 164% on day 21 in the scaffolds with ES particles, and up to 567 ± 217% on day 14 in the scaffolds with NTES particles (p = .006 and p = .002, respectively, relative to day 0). Overall, this study shows that the physicochemical properties of the alginate-chitosan hydrogel scaffolds with ES or NTES particles are similar to those of cancellous bone. In addition, scaffolds with particles supported early osteogenic differentiation and therefore represent a promising new bone substitute, especially for non-load bearing applications.

Analyzing Sex-Specific Dimorphism in Human Skeletal Stem Cells

Sex-related differences are a current topic in contemporary science. In addition to hormonal regulation, cell-autonomous mechanisms are important in bone homeostasis and regeneration. In this study, human skeletal stem cells (SSCs) from female and male adults were cultured and analyzed with immunological assays and osteogenic differentiation assessments. Female SSCs exhibited a mean doubling time of 100.6 h, whereas male SSCs displayed a mean doubling time of 168.0 h. Immunophenotyping revealed the expression of the stem cell markers Nestin, CD133, and CD164, accompanied by the neural-crest marker SOX9. Furthermore, multiparameter flow cytometric analyses revealed a substantial population of multipotent SSCs, comprising up to 80% in both sexes. An analysis of the osteogenic differentiation potential demonstrated a strong mineralization in both male and female SSCs under physiological conditions. Recognizing the prevailing association of bone diseases with inflammatory processes, we also analyzed the osteogenic potential of SSCs from both sexes under pro-inflammatory conditions. Upon TNF-α and IL-1β treatment, we observed no sexual dimorphism on osteogenesis. In summary, we demonstrated the successful isolation and characterization of SSCs capable of rapid osteogenic differentiation. Taken together, in vitro cultured SSCs might be a suitable model to study sexual dimorphisms and develop drugs for degenerative bone diseases.

Fabrication of a three-dimensional bone marrow niche-like acute myeloid Leukemia disease model by an automated and controlled process using a robotic multicellular bioprinting system

BACKGROUND

Acute myeloid leukemia (AML) is a hematological malignancy that remains a therapeutic challenge due to the high incidence of disease relapse. To better understand resistance mechanisms and identify novel therapies, robust preclinical models mimicking the bone marrow (BM) microenvironment are needed. This study aimed to achieve an automated fabrication process of a three-dimensional (3D) AML disease model that recapitulates the 3D spatial structure of the BM microenvironment and applies to drug screening and investigational studies.

METHODS

To build this model, we investigated a unique class of tetramer peptides with an innate ability to self-assemble into stable hydrogel. An automated robotic bioprinting process was established to fabricate a 3D BM (niche-like) multicellular AML disease model comprised of leukemia cells and the BM's stromal and endothelial cellular fractions. In addition, monoculture and dual-culture models were also fabricated. Leukemia cell compatibility, functionalities (in vitro and in vivo), and drug assessment studies using our model were performed. In addition, RNAseq and gene expression analysis using TaqMan arrays were also performed on 3D cultured stromal cells and primary leukemia cells.

RESULTS

The selected peptide hydrogel formed a highly porous network of nanofibers with mechanical properties similar to the BM extracellular matrix. The robotic bioprinter and the novel quadruple coaxial nozzle enabled the automated fabrication of a 3D BM niche-like AML disease model with controlled deposition of multiple cell types into the model. This model supported the viability and growth of primary leukemic, endothelial, and stromal cells and recapitulated cell-cell and cell-ECM interactions. In addition, AML cells in our model possessed quiescent characteristics with improved chemoresistance attributes, resembling more the native conditions as indicated by our in vivo results. Moreover, the whole transcriptome data demonstrated the effect of 3D culture on enhancing BM niche cell characteristics. We identified molecular pathways upregulated in AML cells in our 3D model that might contribute to AML drug resistance and disease relapse.

CONCLUSIONS

Our results demonstrate the importance of developing 3D biomimicry models that closely recapitulate the in vivo conditions to gain deeper insights into drug resistance mechanisms and novel therapy development. These models can also improve personalized medicine by testing patient-specific treatments.

Transcriptomics reveals the molecular regulation of Chinese medicine formula on improving bone quality in broiler

Skeletal disorder is of concern to the poultry industry as it affects animal welfare and production performance. Traditional Chinese medicine could improve bone quality and reduce the incidence of bone disease, but the molecular regulation of Chinese medicine formula (CMF) on improving bone quality in broilers is still unclear. This study was performed to research the effects of CMF on skeletal performance of Cobb broilers and reveal the molecular regulation. A total of 120 one-day-old Cobb broilers were randomly allocated into 4 equal groups of 30 chickens, with 5 replicates and 6 chickens in each replicate. The control (CON) group was fed a diet without CMF, while the CMF1, CMF2, and CMF3 groups were supplemented with different CMF at 6,000 mg/kg diet, respectively. The broilers were raised to 60 d of age, then bone tissues were collected for biomechanical properties, micro-CT detection and transcriptomic sequencing analysis. The results showed that CMF3 improved the biomechanical properties of broiler tibia, via increasing the elastic modulus (P < 0.05), yield strength (P > 0.05), maximum stress (P < 0.05) and fracture stress (P < 0.05) of the tibia. Micro-CT analysis indicated that CMF3 increased the bone mineral density (BMD), bone volume/total volume (BV/TV), bone surface density (BS/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and decreased the trabecular separation (Tb.Sp) of femur cancellous bone (P < 0.05). RNA-seq analysis revealed 2,177 differentially expressed genes (DEGs) (|log2FoldChange| ≥ 1, FDR < 0.05) between the CMF3 group and CON group. Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) analysis showed 13 pathways mostly associated with bone growth and development and bone metabolism, and we identified 39 bone-related DEGs. This study suggests that CMF3 could improve bone strength and bone microstructure of broilers, and showed a positive effect on bone performance. Our research could provide a theoretical reference for the development of pollution-free feed additives to improve the skeletal performance of broilers, which could help promote healthy farming of chickens.

Potential Joint Protective and Anti-Inflammatory Effects of Integrin αvβ3 in IL-1β-Treated Chondrocytes Cells

In osteoarthritis (OA), the articular cartilage covering the articular surface of the bone wears out, exposing the subchondral bone, and the synovial membrane surrounding the joint becomes inflamed, causing pain and deformity. OA causes pain, stiffness, and swelling, and discomfort in the knee when climbing stairs is a typical symptom. Although drug development studies are conducted to treat these inflammatory joint diseases, it is difficult to find conclusive research results which could reduce inflammation and slow cartilage tear. The development of drugs to relieve inflammatory pain often utilizes inflammatory triggers. Interleukins, one of the proteins in the limelight as pro-inflammatory factors, are immune-system-stimulating factors that promote the body's fight against harmful factors such as bacteria. In this study, inflammation was induced in Chondrocytes cells (Chon-001 cells) with IL-1β and then treated with integrin αvβ3 to show anti-inflammatory and chondrogenesis effects. Integrin αvβ3 was not toxic to Chon-001 cells in any concentration groups treated with or without IL-1β. COX-2 and iNOS, which are major markers of inflammation, were significantly reduced by integrin αvβ3 treatment. Expressions of p-ERK, p-JNK, and p-p38 corresponding to the MAPKs signaling pathway and p-IκBα and p-p65 corresponding to the NF-κB signaling pathway were also decreased in a dose-dependent manner upon integrin αvβ3 treatment, indicating that inflammation was inhibited, whereas treatment with integrin αvβ3 significantly increased the expression of ALP, RUNX2, BMP2, BMP4, Aggrecan, SOX9, and COL2A1, suggesting that osteogenesis and chondrogenesis were induced. These results suggest that integrin αvβ3 in-duces an anti-inflammatory effect, osteogenesis, and chondrogenesis on IL-1β-induced Chon-001 cells.

Development, Establishment, and Validation of a Model for the Mineralization of Periodontium Remodelling Cells: Cementoblasts

Chronic kidney disease (CKD) patients undergoing dialysis are at high risk of bone fractures. CKD-induced mineral and bone disorder is extended to periodontal disease due to changes in the ionic composition of saliva in CKD patients, dysregulating mineralization, hindering regeneration and thereby promoting the progression of dental complications. Despite the importance of cementum for overall oral health, the mechanisms that regulate its development and regeneration are not well comprehended, and a lack of sufficient in vitro experimental models has hindered research progress. In this study, the impact of experimental conditions on the calcification of cementoblasts was systematically investigated, aimed at establishing a standardized and validated model for the calcification of cementoblasts. The effects of phosphate, calcium, ascorbic acid, β-glycerolphosphate, dexamethasone, and fetal calf serum on the calcification process of cementoblasts were analyzed over a wide range of concentrations and time points by investigating calcium content, cell viability, gene expression and kinase activity. Cementoblasts calcified in a concentration- and time-dependent manner with higher concentrations of supplements cause a higher degree of calcification but decreased cell viability. Phosphate and calcium have a significantly stronger effect on cementoblast calcification processes compared to osteogenic supplements: ascorbic acid, β-glycerolphosphate, and dexamethasone induce calcification over a wide range of osteogenic signalling pathways, with osteopontin being a central target of gene regulation. Conversely, treatment with ascorbic acid, β-glycerolphosphate, and dexamethasone leads to activating only selected pathways, especially promoting bone sialoprotein expression. The developed and validated cementoblast calcification protocol, incubating up to 60% confluent cementoblasts with 1.9 mmol L-1 of phosphate supplementation for a reasonable, multi-pathway calcification induction and 10 mmol L-1 β-glycerolphosphate, 75 µmol L-1 ascorbic acid and 10 nmol L-1 dexamethasone for a reasonable osteogenic differentiation-based calcification induction, provides standard in vitro experimental models for better understanding cementoblast function and regeneration.

Dissection of Cellular Communication between Human Primary Osteoblasts and Bone Marrow Mesenchymal Stem Cells in Osteoarthritis at Single-Cell Resolution

Background and Objectives

Osteoblasts are derived from bone marrow mesenchymal stem cells (BMMSCs) and play important role in bone remodeling. While our previous studies have investigated the cell subtypes and heterogeneity in osteoblasts and BMMSCs separately, cell-to-cell communications between osteoblasts and BMMSCs in vivo in humans have not been characterized. The aim of this study was to investigate the cellular communication between human primary osteoblasts and bone marrow mesenchymal stem cells.

Methods and Results

To investigate the cell-to-cell communications between osteoblasts and BMMSCs and identify new cell subtypes, we performed a systematic integration analysis with our single-cell RNA sequencing (scRNA-seq) transcriptomes data from BMMSCs and osteoblasts. We successfully identified a novel preosteoblasts subtype which highly expressed ATF3, CCL2, CXCL2 and IRF1. Biological functional annotations of the transcriptomes suggested that the novel preosteoblasts subtype may inhibit osteoblasts differentiation, maintain cells to a less differentiated status and recruit osteoclasts. Ligand-receptor interaction analysis showed strong interaction between mature osteoblasts and BMMSCs. Meanwhile, we found FZD1 was highly expressed in BMMSCs of osteogenic differentiation direction. WIF1 and SFRP4, which were highly expressed in mature osteoblasts were reported to inhibit osteogenic differentiation. We speculated that WIF1 and sFRP4 expressed in mature osteoblasts inhibited the binding of FZD1 to Wnt ligand in BMMSCs, thereby further inhibiting osteogenic differentiation of BMMSCs.

Conclusions

Our study provided a more systematic and comprehensive understanding of the heterogeneity of osteogenic cells. At the single cell level, this study provided insights into the cell-to-cell communications between BMMSCs and osteoblasts and mature osteoblasts may mediate negative feedback regulation of osteogenesis process.

Effect of Expansion Media on Functional Characteristics of Bone Marrow-Derived Mesenchymal Stromal Cells

The therapeutic efficacy of mesenchymal stromal cells (MSCs) has been shown to rely on their immunomodulatory and regenerative properties. In order to obtain sufficient numbers of cells for clinical applications, MSCs have to be expanded ex vivo. Expansion media with xenogeneic-free (XF) growth-promoting supplements like human platelet lysate (PL) or serum- and xenogeneic-free (SF/XF) formulations have been established as safe and efficient, and both groups provide different beneficial qualities. In this study, MSCs were expanded in XF or SF/XF media as well as in mixtures thereof. MSCs cultured in these media were analyzed for phenotypic and functional properties. MSC expansion was optimal with SF/XF conditions when PL was present. Metabolic patterns, consumption of growth factors, and secretome of MSCs differed depending on the type and concentration of supplement. The lactate per glucose yield increased along with a higher proportion of PL. Many factors in the supernatant of cultured MSCs showed distinct patterns depending on the supplement (e.g., FGF-2, TGFβ, and insulin only in PL-expanded MSC, and leptin, sCD40L PDGF-AA only in SF/XF-expanded MSC). This also resulted in changes in cell characteristics like migratory potential. These findings support current approaches where growth media may be utilized for priming MSCs for specific therapeutic applications.

The Role of Osteopontin in Respiratory Health and Disease

The biological functions of osteopontin (OPN) are diverse and specific to physiological and pathophysiological conditions implicated in inflammation, biomineralization, cardiovascular diseases, cellular viability, cancer, diabetes, and renal stone disease. We aimed to present the role of OPN in respiratory health and disease. OPN influences the immune system and is a chemo-attractive protein correlated with respiratory disease severity. There is evidence that OPN can advance the disease stage associated with its fibrotic, inflammatory, and immune functions. OPN contributes to eosinophilic airway inflammation. OPN can destroy the lung parenchyma through its neutrophil influx and fibrotic mechanisms, linking OPN to at least one of the two major chronic obstructive pulmonary disease phenotypes. Respiratory diseases that involve irreversible lung scarring, such as idiopathic pulmonary disease, are linked to OPN, with protein levels being overexpressed in individuals with severe or advanced stages of the disorders and considerably lower levels in those with less severe symptoms. OPN plays a significant role in lung cancer progression and metastasis. It is also implicated in the pathogenesis of pulmonary hypertension, coronavirus disease 2019, and granuloma generation.

A New Perspective on Metabolic Syndrome with Osteopontin: A Comprehensive Review

Metabolic syndrome (MetS) imposes a substantial burden on the healthcare systems and economies of countries and is a major public health concern worldwide. MetS is mainly caused by an imbalance between calorie intake and energy expenditure; however, it is recognized that additional variables, such as chronic inflammation, may have the same predictive potential as insulin resistance or MetS components in the genesis of type 2 diabetes and cardiovascular events. More importantly, the early diagnosis or treatment of MetS may significantly reduce the burden on the health systems of the disease with any prevention or biomarker and should not be underestimated. Osteopontin (OPN), also called secreted phosphoprotein 1, is a soluble protein found mostly in body fluids. Studies suggest that serum OPN levels may be an early and new biomarker to predict metabolic and cardiovascular complications significantly associated with some diseases. This review aims to provide specific insight into the new biomarker OPN in MetS. With this purpose, it is examined the link between the MetS cornerstones and OPN. In addition, the interaction between the microbiota and MetS is predicted to be bidirectional, and the microbiota may act as a bridge in this interaction process. Increased OPN levels may have unfavourable consequences for cardiovascular diseases, diabetes, and obesity, all of which are components of MetS. Further studies are required to evaluate the use of OPN levels as a clinical biomarker risk of MetS.

Meta-analysis of RNA-Seq datasets highlights novel genes/pathways involved in fat deposition in fat-tail of sheep

Introduction

Fat-tail in sheep is considered as an important energy reservoir to provide energy as a survival buffer during harsh challenges. However, fat-tail is losing its importance in modern sheep industry systems and thin-tailed breeds are more desirable. Using comparative transcriptome analysis to compare fat-tail tissue between fat- and thin-tailed sheep breeds provides a valuable approach to study the complex genetic factors associated with fat-tail development. However, transcriptomic studies often suffer from issues with reproducibility, which can be improved by integrating multiple studies based on a meta-analysis.

Methods

Hence, for the first time, an RNA-Seq meta-analysis on sheep fat-tail transcriptomes was performed using six publicly available datasets.

Results and discussion

A total of 500 genes (221 up-regulated, 279 down-regulated) were identified as differentially expressed genes (DEGs). A jackknife sensitivity analysis confirmed the robustness of the DEGs. Moreover, QTL and functional enrichment analysis reinforced the importance of the DEGs in the underlying molecular mechanisms of fat deposition. Protein-protein interactions (PPIs) network analysis revealed the functional interactions among the DEGs and the subsequent sub-network analysis led to identify six functional sub-networks. According to the results of the network analysis, down-regulated DEGs in green and pink sub-networks (like collagen subunits IV, V, and VI, integrins 1 and 2, SCD, SCD5, ELOVL6, ACLY, SLC27A2, and LPIN1) may impair lipolysis or fatty acid oxidation and cause fat accumulation in tail. On the other hand, up-regulated DEGs, especially those are presented in green and pink sub-networks (like IL6, RBP4, LEPR, PAI-1, EPHX1, HSD11B1, and FMO2), might contribute to a network controlling fat accumulation in the tail of sheep breed through mediating adipogenesis and fatty acid biosynthesis. Our results highlighted a set of known and novel genes/pathways associated with fat-tail development, which could improve the understanding of molecular mechanisms behind fat deposition in sheep fat-tail.

Visceral mesenchymal stem cells from type 2 diabetes donors activate triglycerides synthesis in healthy adipocytes via metabolites exchange and cytokines secretion

BACKGROUND

In recent years, there has been an increase in the prevalence of obesity and type 2 diabetes mellitus (T2DM). Development of visceral instead of subcutaneous adipose tissue is pathogenic and increases the risk of metabolic abnormalities. We hypothesize that visceral adipocytes and stromal cells are able to deteriorate other fat depots metabolism via secretory mechanisms.

METHODS

We study the regulatory role of visceral adipose-derived stem cells (vADSC) from donors with obesity and T2DM or normal glucose tolerance (NGT) on healthy subcutaneous ADSC (sADSC) in the Transwell system. Lipid droplets formation during adipogenesis was assessed by confocal microscopy. Cell metabolism was evaluated by 14C-glucose incorporation analysis and western blotting. vADSC secretome was assessed by Milliplex assay.

RESULTS

We showed that both NGT and T2DM vADSC had mesenchymal phenotype, but expression of CD29 was enhanced, whereas expressions of CD90, CD140b and IGF1R were suppressed in both NGT and T2DM vADSC. Co-differentiation with T2DM vADSC increased lipid droplet size and stimulated accumulation of fatty acids in adipocytes from healthy sADSC. In mature adipocytes T2DM vADSC stimulated triglyceride formation, whereas NGT vADSC activated oxidative metabolism. Secretome of NGT vADSC was pro-inflammatory and pro-angiogenic in comparison with T2DM vADSC.

CONCLUSIONS

The present study has demonstrated the critical role of secretory interactions between visceral and subcutaneous fat depots both in the level of progenitor and mature cells. Mechanisms of these interactions are related to direct exchange of metabolites and cytokines secretion.

Sema7A protects against high-fat diet-induced obesity and hepatic steatosis by regulating adipo/lipogenesis

OBJECTIVE

Obesity and related diseases are becoming a growing risk for public health around the world due to the westernized lifestyle. Sema7A, an axonal guidance molecule, has been known to play a role in neurite growth, bone formation, and immune regulation. Whether Sema7A participates in obesity and metabolic diseases is unknown. As several SNPs in SEMA7A and its receptors were found to correlate with BMI and metabolic parameters in the human population, we investigated the potential role of Sema7A in obesity and hepatic steatosis.

METHODS

GWAS and GEPIA database was used to analyze SNPs in SEMA7A and the correlation of Sema7A expression with lipid metabolism related genes. Sema7A-/- mice and recombinant Sema7A (rSema7A) were used to study the role of Sema7A in HFD-induced obesity and hepatic steatosis. Adipose tissue-derived mesenchymal stem cells (ADSCs) were used to examine the role of Sema7A in adipogenesis, lipogenesis and downstream signaling.

RESULTS

Deletion of Sema7A aggravated HFD-induced obesity. Sema7A deletion enhanced adipogenesis in both subcutaneous and visceral ADSCs, while the addition of rSema7A inhibited adipogenesis of ADSCs and lipogenesis of differentiated mature adipocytes. Sema7A inhibits adipo/lipogenesis potentially through its receptor integrin β1 and downstream FAK signaling. Importantly, administration of rSema7A had protective effects against diet-induced obesity in mice. In addition, deletion of Sema7A led to increased hepatic steatosis and insulin resistance in mice.

CONCLUSIONS

Our findings reveal a novel inhibitory role of Sema7A in obesity and hepatic steatosis, providing a potential new therapeutic target for obesity and metabolic diseases.

The roles of bone remodeling in normal hematopoiesis and age-related hematological malignancies

Prior research establishing that bone interacts in coordination with the bone marrow microenvironment (BMME) to regulate hematopoietic homeostasis was largely based on analyses of individual bone-associated cell populations. Recent advances in intravital imaging has suggested that the expansion of hematopoietic stem cells (HSCs) and acute myeloid leukemia cells is restricted to bone marrow microdomains during a distinct stage of bone remodeling. These findings indicate that dynamic bone remodeling likely imposes additional heterogeneity within the BMME to yield differential clonal responses. A holistic understanding of the role of bone remodeling in regulating the stem cell niche and how these interactions are altered in age-related hematological malignancies will be critical to the development of novel interventions. To advance this understanding, herein, we provide a synopsis of the cellular and molecular constituents that participate in bone turnover and their known connections to the hematopoietic compartment. Specifically, we elaborate on the coupling between bone remodeling and the BMME in homeostasis and age-related hematological malignancies and after treatment with bone-targeting approaches. We then discuss unresolved questions and ambiguities that remain in the field.

Lactoferrin, Osteopontin and Lactoferrin–Osteopontin Complex: A Critical Look on Their Role in Perinatal Period and Cardiometabolic Disorders

Milk-derived bioactive proteins have increasingly gained attention and consideration throughout the world due to their high-quality amino acids and multiple health-promoting attributes. Apparently, being at the forefront of functional foods, these bioactive proteins are also suggested as potential alternatives for the management of various complex diseases. In this review, we will focus on lactoferrin (LF) and osteopontin (OPN), two multifunctional dairy proteins, as well as to their naturally occurring bioactive LF–OPN complex. While describing their wide variety of physiological, biochemical, and nutritional functionalities, we will emphasize their specific roles in the perinatal period. Afterwards, we will evaluate their ability to control oxidative stress, inflammation, gut mucosal barrier, and intestinal microbiota in link with cardiometabolic disorders (CMD) (obesity, insulin resistance, dyslipidemia, and hypertension) and associated complications (diabetes and atherosclerosis). This review will not only attempt to highlight the mechanisms of action, but it will critically discuss the potential therapeutic applications of the underlined bioactive proteins in CMD.

Cyclic di-adenosine monophosphate regulates the osteogenic and adipogenic differentiation of hPDLSCs via MAPK and NF-κB signaling

Cyclic di-adenosine monophosphate (c-di-AMP) is a bacterial second messenger that can be recognized by infected host cells and activate the immunoinflammatory response. The purpose of this study is to demonstrate the effect of c-di-AMP on the differentiation of human periodontal ligament stem cells (hPDLSCs) and its underlying mechanisms. In the present study, we find that the gingival crevicular fluid (GCF) of patients with chronic periodontitis has a higher expression level of c-di-AMP than that of healthy people. In vitro, c-di-AMP influences the differentiation of hPDLSCs by upregulating Toll-like receptors (TLRs); specifically, it inhibits osteogenic differentiation by activating NF-κB and ERK/MAPK and promotes adipogenic differentiation through the NF-κB and p38/MAPK signaling pathways. Inhibitors of TLRs or activated pathways reduce the changes induced by c-di-AMP. Our results establish the potential correlation among bacterial c-di-AMP, periodontal tissue homeostasis and chronic periodontitis pathogenesis.

Preparation and In Vitro Evaluation of Chitosan-g-Oligolactide Based Films and Macroporous Hydrogels for Tissue Engineering

In the current study, novel matrices based on chitosan-g-oligo (L,L-/L,D-lactide) copolymers were fabricated. In particular, 2D films were prepared by solvent casting, while 3D macroporous hydrogels were obtained by lyophilization of copolymer solutions. Copolymers of chitosan (Chit) with semi-crystalline oligo (L,L-lactide) (Chit-LL) or amorphous oligo (L,D-lactide) (Chit-LD) were obtained by solid-state mechanochemical synthesis. The structure of the hydrogels was found to be a system of interconnected macropores with an average size of 150 μm. In vitro degradation of these copolymer-based matrices was shown to increase in the case of the Chit-LL-based hydrogel by 34% and decrease for the Chit-LD-based hydrogel by 23% compared to the parameter of the Chit sample. Localization and distribution of mouse fibroblast L929 cells and adipose tissue-derived mesenchymal stromal cells (MSCs) within the hydrogels was studied by confocal laser scanning microscopy (CLSM). Moreover, cellular response, namely cell adhesion, spreading, growth, proliferation, as well as cell differentiation in vitro were also evaluated in the hydrogels for 10-14 days. Both the Chit-LL and Chit-LD matrices were shown to support cell growth and proliferation, while they had improved swelling compared to the Chit matrix. Osteogenic MSCs differentiation on the copolymer-based films was studied by quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR). Maximal expression levels of osteogenesis markers (alkaline phosphatase (ALPL), bone transcription factor (Runx2), and osteopontin (SPP1) were revealed for the Chit-LD films. Thus, osteodifferentiation was demonstrated to depend on the film composition. Both Chit-LL and Chit-LD copolymer-based matrices are promising for tissue engineering.

Early osteoimmunomodulation by mucin hydrogels augments the healing and revascularization of rat critical-size calvarial bone defects

The design principle of osteogenic bone grafts has shifted from immunological inertness to limiting foreign body response to combined osteoimmunomodulatory activity to promote high-quality endogenous bone regeneration. Recently developed immunomodulatory mucin hydrogels have been shown to elicit very low complement activation and suppress macrophage release and activation after implantation in vivo. However, their immunoregulatory activity has not yet been studied in the context of tissue repair. Herein, we synthesized mucin-monetite composite materials and investigated their early osteoimmunomodulation using a critical-size rat bone defect model. We demonstrated that the composites can polarize macrophages towards the M2 phenotype at weeks 1 and 2. The early osteoimmunomodulation enhanced early osteogenesis and angiogenesis and ultimately promoted fracture healing and engraftment (revascularization of the host vasculature) at weeks 6 and 12. Overall, we demonstrated the applicability of mucin-based immunomodulatory biomaterials to enhance tissue repair in tissue engineering and regenerative medicine.

Aging and Bone Metabolism

Changes in bone architecture and metabolism with aging increase the likelihood of osteoporosis and fracture. Age-onset osteoporosis is multifactorial, with contributory extrinsic and intrinsic factors including certain medical problems, specific prescription drugs, estrogen loss, secondary hyperparathyroidism, microenvironmental and cellular alterations in bone tissue, and mechanical unloading or immobilization. At the histological level, there are changes in trabecular and cortical bone as well as marrow cellularity, lineage switching of mesenchymal stem cells to an adipogenic fate, inadequate transduction of signals during skeletal loading, and predisposition toward senescent cell accumulation with production of a senescence-associated secretory phenotype. Cumulatively, these changes result in bone remodeling abnormalities that over time cause net bone loss typically seen in older adults. Age-related osteoporosis is a geriatric syndrome due to the multiple etiologies that converge upon the skeleton to produce the ultimate phenotypic changes that manifest as bone fragility. Bone tissue is dynamic but with tendencies toward poor osteoblastic bone formation and relative osteoclastic bone resorption with aging. Interactions with other aging physiologic systems, such as muscle, may also confer detrimental effects on the aging skeleton. Conversely, individuals who maintain their BMD experience a lower risk of fractures, disability, and mortality, suggesting that this phenotype may be a marker of successful aging. © 2023 American Physiological Society. Compr Physiol 13:4355-4386, 2023.

Impact of a modified implant macrogeometry on biomechanical parameters and bone-related markers in rats

This study investigated the impact of a modified implant macrogeometry on peri-implant healing and its effect on bone-related molecules in rats. Eighteen rats received one implant in each tibia: the control group received implants with conventional macrogeometry and the test group received implants with modified macrogeometry. After 30 days, the implants were removed for biomechanical analysis and the bone tissue around them was collected for quantifying gene expression of OPN, Runx2, β-catenin, BMP-2, Dkk1, and RANKL/OPG. Calcein and tetracycline fluorescent markers were used for analyzing newly formed bone at undecalcified sections of the tibial implants. These fluorescent markers showed continuous bone formation at cortical bone width and sparse new bone formed along the medullary implant surface in both groups. However, higher counter-torque values and upregulation of OPN expression were achieved by test implants when compared to controls. The modified macrogeometry of implants optimized peri-implant healing, favoring the modulation of OPN expression in the osseous tissue around the implants.

Osteometabolism: Metabolic Alterations in Bone Pathologies

Renewing interest in the study of intermediate metabolism and cellular bioenergetics is brought on by the global increase in the prevalence of metabolic illnesses. Understanding of the mechanisms that integrate energy metabolism in the entire organism has significantly improved with the application of contemporary biochemical tools for quantifying the fuel substrate metabolism with cutting-edge mouse genetic procedures. Several unexpected findings in genetically altered mice have prompted research into the direction of intermediate metabolism of skeletal cells. These findings point to the possibility of novel endocrine connections through which bone cells can convey their energy status to other metabolic control centers. Understanding the expanded function of skeleton system has in turn inspired new lines of research aimed at characterizing the energy needs and bioenergetic characteristics of these bone cells. Bone-forming osteoblast and bone-resorbing osteoclast cells require a constant and large supply of energy substrates such as glucose, fatty acids, glutamine, etc., for their differentiation and functional activity. According to latest research, important developmental signaling pathways in bone cells are connected to bioenergetic programs, which may accommodate variations in energy requirements during their life cycle. The present review article provides a unique perspective of the past and present research in the metabolic characteristics of bone cells along with mechanisms governing energy substrate utilization and bioenergetics. In addition, we discussed the therapeutic inventions which are currently being utilized for the treatment and management of bone-related diseases such as osteoporosis, rheumatoid arthritis (RA), osteogenesis imperfecta (OIM), etc., by modulating the energetics of bone cells. We further emphasized on the role of GUT-associated metabolites (GAMs) such as short-chain fatty acids (SCFAs), medium-chain fatty acids (MCFAs), indole derivates, bile acids, etc., in regulating the energetics of bone cells and their plausible role in maintaining bone health. Emphasis is importantly placed on highlighting knowledge gaps in this novel field of skeletal biology, i.e., "Osteometabolism" (proposed by our group) that need to be further explored to characterize the physiological importance of skeletal cell bioenergetics in the context of human health and bone related metabolic diseases.

Enhanced osteogenic differentiation of human mesenchymal stem cells using size-controlled graphene oxide flakes

Recently, it has been revealed that the physical microenvironment can be translated into cellular mechanosensing to direct human mesenchymal stem cell (hMSC) differentiation. Graphene oxide (GO), a major derivative of graphene, has been regarded as a promising material for stem cell lineage specification due to its biocompatibility and unique physical properties to interact with stem cells. Especially, the lateral size of GO flakes is regarded as the key factor regulating cellular response caused by GO. In this work, GO that had been mechanically created and had an average diameter of 0.9, 1.1, and 1.7 m was produced using a ball-mill process. When size-controlled GO flakes were applied to hMSCs, osteogenic differentiation was enhanced by GO with a specific average diameter of 1.7 μm. It was confirmed that osteogenic differentiation was increased due to the enhanced expression of focal adhesion and the development of focal adhesion subordinate signals via extracellular signal-regulated kinase (ERK)-mitogen-activated protein kinase (MEK) pathway. These results suggest that size-controlled GO flakes could be efficient materials for promoting osteogenesis of hMSCs. Results of this study could also improve our understanding of the correlation between hMSCs and cellular responses to GO.

CTR9 drives osteochondral lineage differentiation of human mesenchymal stem cells via epigenetic regulation of BMP-2 signaling

Cell fate determination of human mesenchymal stem/stromal cells (hMSCs) is precisely regulated by lineage-specific transcription factors and epigenetic enzymes. We found that CTR9, a key scaffold subunit of polymerase-associated factor complex (PAFc), selectively regulates hMSC differentiation to osteoblasts and chondrocytes, but not to adipocytes. An in vivo ectopic osteogenesis assay confirmed the essentiality of CTR9 in hMSC-derived bone formation. CTR9 counteracts the activity of Enhancer Of Zeste 2 (EZH2), the epigenetic enzyme that deposits H3K27me3, in hMSCs. Accordingly, CTR9 knockdown (KD) hMSCs gain H3K27me3 mark, and the osteogenic differentiation defects of CTR9 KD hMSCs can be partially rescued by treatment with EZH2 inhibitors. Transcriptome analyses identified bone morphology protein-2 (BMP-2) as a downstream effector of CTR9. BMP-2 secretion, membrane anchorage, and the BMP-SMAD pathway were impaired in CTR9 KD MSCs, and the effects were rescued by BMP-2 supplementation. This study uncovers an epigenetic mechanism engaging the CTR9-H3K27me3-BMP-2 axis to regulate the osteochondral lineage differentiation of hMSCs.

Lineage-selective super enhancers mediate core regulatory circuitry during adipogenic and osteogenic differentiation of human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) can be differentiated into osteoblasts and adipocytes. During these processes, super enhancers (SEs) play important roles. Here, we performed comprehensive characterization of the SEs changes associated with adipogenic and osteogenic differentiation of hMSCs, and revealed that SEs changed more dramatically compared with typical enhancers. We identified a set of lineage-selective SEs, whose target genes were enriched with cell type-specific functions. Functional experiments in lineage-selective SEs demonstrated their specific roles in directed differentiation of hMSCs. We also found that some key transcription factors regulated by lineage-selective SEs could form core regulatory circuitry (CRC) to regulate each other's expression and control the hMSCs fate determination. In addition, we found that GWAS SNPs of osteoporosis and obesity were significantly enriched in osteoblasts-selective SEs or adipocytes-selective SEs, respectively. Taken together, our studies unveiled important roles of lineage-selective SEs in hMSCs differentiation into osteoblasts and adipocytes.

The Effect of a Comprehensive Life-Style Intervention Program of Diet and Exercise on Four Bone-Derived Proteins, FGF-23, Osteopontin, NGAL and Sclerostin, in Overweight or Obese Children and Adolescents

The adipose and bone tissues demonstrate considerable interconnected endocrine function. In the present study, we determined the concentrations of fibroblast growth factor-23 (FGF-23), osteopontin, neutrophil gelatinase-associated lipocalin (NGAL) and sclerostin in 345 children and adolescents who were overweight or obese (mean age ± SD mean: 10.36 ± 0.16 years; 172 males, 173 females; 181 prepubertal; and 164 pubertal) before and after their participation in a comprehensive life-style intervention program of diet and exercise for one year. Following the one-year life-style interventions, there was a significant decrease in BMI (p < 0.01), FGF-23 (p < 0.05), osteopontin (p < 0.01) and NGAL (p < 0.01), and an increase in sclerostin (p < 0.01) concentrations. BMI z-score (b = 0.242, p < 0.05) and fat mass (b = 0.431, p < 0.05) were the best positive predictors and waist-to-height ratio (WHtR) (b = −0.344, p < 0.05) was the best negative predictor of the change of osteopontin. NGAL concentrations correlated positively with HbA1C (b = 0.326, p < 0.05), WHtR (b = 0.439, p < 0.05) and HOMA-IR (b = 0.401, p < 0.05), while BMI (b = 0.264, p < 0.05), fat mass (b = 1.207, p < 0.05), HDL (b = 0.359, p < 0.05) and waist circumference (b = 0.263, p < 0.05) were the best positive predictors of NGAL. These results indicate that FGF-23, osteopontin, NGAL and sclerostin are associated with being overweight or obese and are altered in relation to alterations in BMI. They also indicate a crosstalk between adipose tissue and bone tissue and may play a role as potential biomarkers of glucose metabolism. Further studies are required to delineate the physiological mechanisms underlying this association in children and adolescents.

Spatial Delivery of Triple Functional Nanoparticles via an Extracellular Matrix-Mimicking Coaxial Scaffold Synergistically Enhancing Bone Regeneration

It remains a major challenge to simultaneously achieve bone regeneration and prevent infection in the complex microenvironment of repairing bone defects. Here, we developed a novel ECM-mimicking scaffold by coaxial electrospinning to be endowed with multibiological functions. Lysophosphatidic acid (LPA) and zinc oxide (ZnO) nanoparticles were loaded into the poly-lactic-co-glycolic acid/polycaprolactone (PLGA/PCL, PP) sheath layer of coaxial nanofibers, and deferoxamine (DFO) nanoparticles were loaded into its core layer. The novel scaffold PP-LPA-ZnO/DFO maintained a porous nanofibrous architecture after incorporating three active nanoparticles, showing better physicochemical properties and eximious biocompatibility. In vitro studies showed that the bio-scaffold loaded with LPA nanoparticles had excellent cell adhesion, proliferation, and differentiation for MC3T3-E1 cells and synergistic osteogenesis with the addition of ZnO and DFO nanoparticles. Further, the PP-LPA-ZnO/DFO scaffold promoted tube formation and facilitated the expression of vascular endothelial markers in HUVECs. In vitro antibacterial studies against Escherichia Coli and Staphylococcus aureus demonstrated effective antibacterial activity of the PP-LPA-ZnO/DFO scaffold. In vivo studies showed that the PP-LPA-ZnO/DFO scaffold exhibited excellent biocompatibility after subcutaneous implantation and remarkable osteogenesis at 4 weeks post-implantation in the mouse alveolar bone defects. Importantly, the PP-LPA-ZnO/DFO scaffold showed significant antibacterial activity, prominent neovascularization, and new bone formation in the rat fenestration defect model. Overall, the spatially sustained release of LPA, ZnO, and DFO nanoparticles through the coaxial scaffold synergistically enhanced biocompatibility, osteogenesis, angiogenesis, and effective antibacterial properties, which is ultimately beneficial for bone regeneration. This project provides the optimized design of bone regenerative biomaterials and a new strategy for bone regeneration, especially in the potentially infected microenvironment.

Polydopamine-Mediated Protein Adsorption Alters the Epigenetic Status and Differentiation of Primary Human Adipose-Derived Stem Cells (hASCs)

Polydopamine (PDA) is a biocompatible cell-adhesive polymer with versatile applications in biomedical devices. Previous studies have shown that PDA coating could improve cell adhesion and differentiation of human mesenchymal stem cells (hMSCs). However, there is still a knowledge gap in the effect of PDA-mediated protein adsorption on the epigenetic status of MSCs. This work used gelatin-coated cell culture surfaces with and without PDA underlayer (Gel and PDA-Gel) to culture and differentiate primary human adipose-derived stem cells (hASCs). The properties of these two substrates were significantly different, which, in combination with a variation in extracellular matrix (ECM) protein bioactivity, regulated cell adhesion and migration. hASCs reduced focal adhesions by downregulating the expression of integrins such as αV, α1, α2, and β1 on the PDA-Gel compared to the Gel substrate. Interestingly, the ratio of H3K27me3 to H3K27me3+H3K4me3 was decreased, but this only occurred for upregulation of AGG and BMP4 genes during chondrogenic differentiation. This result implies that the PDA-Gel surface positively affects the chondrogenic, but not adipogenic and osteogenic, differentiation. In conclusion, for the first time, this study demonstrates the sequential effects of PDA coating on the biophysical property of adsorbed protein and then focal adhesions and differentiation of hMSCs through epigenetic regulation. This study sheds light on PDA-mediated mechanotransduction.

Does the RGD region of certain proteins affect metabolic activity?

A better understanding of the role of mineralized tissues and their associated factors in governing whole-body metabolism should be of value toward informing clinical strategies to treat mineralized tissue and metabolic disorders, such as diabetes and obesity. This perspective provides evidence suggesting a role for the arginine-glycine-aspartic acid (RGD) region, a sequence identified in several proteins secreted by bone cells, as well as other cells, in modulating systemic metabolic activity. We focus on (a) two of the SIBLING (small integrin-binding ligand, N-linked glycoprotein) family genes/proteins, bone sialoprotein (BSP) and osteopontin (OPN), (b) insulin-like growth factor-binding protein-1 &amp; 2 (IGFBP-1, IGFBP-2) and (c) developmental endothelial locus 1 (DEL1) and milk fat globule–EGF factor-8 (MFG-E8). In addition, for our readers to appreciate the mounting evidence that a multitude of bone secreted factors affect the activity of other tissues, we provide a brief overview of other proteins, to include fibroblast growth factor 23 (FGF23), phosphatase orphan 1 (PHOSPHO1), osteocalcin (OCN/BGLAP), tissue non-specific alkaline phosphatase (TNAP) and acidic serine aspartic-rich MEPE-associated motif (ASARM), along with known/suggested functions of these factors in influencing energy metabolism.

The Role of Osteopontin in Tumor Progression Through Tumor-Associated Macrophages

Osteopontin (OPN) is a multifunctional phosphorylated protein. It is widely involved in solid tumor progression, such as intensification of macrophage recruitment, inhibition of T-cell activity, aggravation of tumor interstitial fibrosis, promotion of tumor metastasis, chemotherapy resistance, and angiogenesis. Most of these pathologies are affected by tumor-associated macrophages (TAMs), an important component of the tumor microenvironment (TME). TAMs have been extensively characterized, including their subsets, phenotypes, activation status, and functions, and are considered a promising therapeutic target for cancer treatment. This review focuses on the interaction between OPN and TAMs in mediating tumor progression. We discuss the strategies for targeting OPN and TAMs to treat cancer and factors that may affect the therapeutic outcomes of blocking OPN or depleting TAMs. We also discuss the role of cancer cell- vs. TAM-derived OPN in tumorigenesis, the mechanisms of how OPN affects TAM recruitment and polarization, and why OPN could mediate anti-tumor and pro-tumor effects, as well as previously reported discrepancies.

Characterization of Dental Pulp Stem Cells Response to Bone Substitutes Biomaterials in Dentistry

Bone substitute biomaterials (BSBs) represent a promising alternative to bone autografts, due to their biocompatibility, osteoconduction, slow resorption rates, and the ability to define and maintain volume for bone gain in dentistry. Many biomaterials are tailored to provide structural and biological support for bone regeneration, and allow the migration of bone-forming cells into the bone defect. Neural crest-derived stem cells isolated from human dental pulp (hDPSCs) represent a suitable stem cell source to study the biological effects of BSBs on osteoprogenitor cells involved in the physiological bone regenerative processes. This study aimed to evaluate how three different BSBs affect the stem cell properties, osteogenic differentiation, and inflammatory properties of hDPSCs. Our data highlight that BSBs do not alter cell proliferation and stemness markers expression, nor induce any inflammatory responses. Bone metabolism data show that hDPSCs exposed to the three BSBs distinctively secrete the factors supporting osteoblast activity and osteoclast activity. Our data indicate that (i) hDPSCs are a suitable stem cell source to study the effects of BSBs, and that (ii) the formulation of BSBs may condition the biological properties of stem cells, suggesting their versatile suitability to different dentistry applications.

The Novel-miR-659/SPP1 Interaction Regulates Fat Deposition in Castrated Male Pigs

Simple Summary

Castration is a standard method for eliminating boar taint in industrial hog production, but it also causes enormous fat accumulation in the carcass. Secreted phosphoprotein 1 (SPP1) was selected to investigate its functions on the regulation of adipose deposition based on our previous data. In the present study, SPP1 overexpression and interference bidirectionally verified that SPP1 inhibited adipogenic differentiation of porcine bone marrow mesenchymal stem cells (pBMSCs). Testosterone-treated cell models were used to simulate the androgen status of intact pigs, and testosterone addition influenced SPP1 mRNA levels during the differentiation of pBMSCs. Moreover, we identified novel-miR-659 and targeted the 3′ untranslated region of SPP1 based on bioinformatics analysis and dual-luciferase assays, and found that the novel-miR-659 upregulation promoted adipogenesis while novel-miR-659 downregulation suppressed adipogenesis in pBMSCs detected by Oil Red O staining and adipogenic markers. Collectively, the interaction between novel-miR-659 and SPP1 can regulate adipose accumulation in castrated male pigs. Our data provide a theoretical basis for further study on the fat deposition mechanism caused by castration.

Abstract

Castration is usually used to remove boar taint in commercial pork production, but the adipose accumulation was increased excessively, which affected the meat quality of pigs. Based on our previous study, secreted phosphoprotein 1 (SPP1) was significantly differentially expressed between castrated and intact male pigs. However, the role of SPP1 in regulating adipose growth and fat storage caused by castration is unknown. In this study, SPP1 was identified to inhibit adipogenesis by the expression of adipogenic markers PPARγ and FABP4 as well as Oil red staining assay during differentiation of porcine bone marrow mesenchymal stem cells (pBMSCs). Subsequently, testosterone was used to treat pBMSCs to simulate the androgen status of intact pigs. Compared with the control groups without testosterone, the SPP1 expression in the testosterone group was markedly increased in the late stage of pBMSCs differentiation. Furthermore, novel-miR-659 was predicted by TargetScan and miRDB to target SPP1 and verified through a dual-luciferase reporter assay. Oil Red O staining assay indicated that novel-miR-659 overexpression significantly promoted adipogenesis, whereas novel-miR-659 inhibition suppressed adipogenesis. The expressions of adipogenic markers PPARγ and FABP4 showed the same tendency. Taken together, our study found that the targeted interaction between novel-miR-659 and SPP1 is involved in regulation of fat deposition in castrated male pigs.

Peri-Implant Repair Using a Modified Implant Macrogeometry in Diabetic Rats: Biomechanical and Molecular Analyses of Bone-Related Markers

DM has a high prevalence worldwide and exerts a negative influence on bone repair around dental implants. Modifications of the microgeometry of implants have been related to positive results in bone repair. This study assessed, for the first time, the influence of an implant with modified macrodesign based on the presence of a healing chamber in the pattern of peri-implant repair under diabetic conditions. Thirty Wistar rats were assigned to receive one titanium implant in each tibia (Control Implant (conventional macrogeometry) or Test Implant (modified macrogeometry)) according to the following groups: Non-DM + Control Implant; Non-DM + Test Implant; DM + Control Implant; DM + Test Implant. One month from the surgeries, the implants were removed for counter-torque, and the bone tissue surrounding the implants was stored for the mRNA quantification of bone-related markers. Implants located on DM animals presented lower counter-torque values in comparison with Non-DM ones, independently of macrodesign (p < 0.05). Besides, higher biomechanical retention levels were observed in implants with modified macrogeometry than in the controls in both Non-DM and DM groups (p < 0.05). Moreover, the modified macrogeometry upregulated OPN mRNA in comparison with the control group in Non-DM and DM rats (p < 0.05). Peri-implant bone repair may profit from the use of implants with modified macrogeometry in the presence of diabetes mellitus, as they offer higher biomechanical retention and positive modulation of important bone markers in peri-implant bone tissue.

Preservation of the naïve features of mesenchymal stromal cells in vitro: Comparison of cell- and bone-derived decellularized extracellular matrix

The fate and behavior of bone marrow mesenchymal stem/stromal cells (BM-MSC) is bidirectionally influenced by their microenvironment, the stem cell niche, where a magnitude of biochemical and physical cues communicate in an extremely orchestrated way. It is known that simplified 2D in vitro systems for BM-MSC culture do not represent their naïve physiological environment. Here, we developed four different 2D cell-based decellularized matrices (dECM) and a 3D decellularized human trabecular-bone scaffold (dBone) to evaluate BM-MSC behavior. The obtained cell-derived matrices provided a reliable tool for cell shape-based analyses of typical features associated with osteogenic differentiation at high-throughput level. On the other hand, exploratory proteomics analysis identified native bone-specific proteins selectively expressed in dBone but not in dECM models. Together with its architectural complexity, the physico-chemical properties of dBone triggered the upregulation of stemness associated genes and niche-related protein expression, proving in vitro conservation of the naïve features of BM-MSC.

Fabrication of Antibacterial, Osteo-Inductor 3D Printed Aerogel-Based Scaffolds by Incorporation of Drug Laden Hollow Mesoporous Silica Microparticles into the Self-Assembled Silk Fibroin Biopolymer

In this study, the novel biomimetic aerogel-based composite scaffolds through a synergistic combination of wet chemical synthesis and advanced engineering approaches have successfully designed. To this aim, initially the photo-crosslinkable methacrylated silk fibroin (SF-MA) biopolymer and methacrylated hollow mesoporous silica microcapsules (HMSC-MA) as the main constituents of the novel composite aerogels were synthesized. Afterward, by incorporation of drug-loaded HMSC-MA into the self-assembled SF-MA, printable gel-based composite inks are developed. By exploiting micro-extrusion-based three-dimensional (3D) printing, SF-MA-HMSC composite gels are printed by careful controlling their viscosity to provide a means to control the shape fidelity of the resulted printed gel constructs. The developed scaffold has shown a multitude of interesting biophysical and biological performances. Namely, thanks to the photo-crosslinking of the gel components during the 3D printing, the scaffolds become mechanically more stable than the pristine SF scaffolds. Also, freeze-casting the printed constructs generates further interconnectivity in the printed pore struts resulting in the scaffolds with hierarchically organized porosities necessary for cell infiltration and growth. Importantly, HMSC incorporated scaffolds promote antibacterial drug delivery, cellular ingrowth and proliferation, promoting osteoblastic differentiation by inducing the expression of osteogenic markers and matrix mineralization. Finally, the osteoconductive, -inductive, and anti-infective composite aerogels are expected to act as excellent bone implanting materials with an extra feature of local and sustained release of drug for efficient therapy of bone-related diseases.

Contrasting effects of <i>Ksr2</i>, an obesity gene, on trabecular bone volume and bone marrow adiposity

Pathological obesity and its complications are associated with an increased propensity for bone fractures. Humans with certain genetic polymorphisms at the kinase suppressor of ras2 (KSR2) locus develop severe early-onset obesity and type 2 diabetes. Both conditions are phenocopied in mice with <i>Ksr2</i> deleted, but whether this affects bone health remains unknown. Here we studied the bones of global <i>Ksr2</i> null mice and found that <i>Ksr2</i> negatively regulates femoral, but not vertebral, bone mass in two genetic backgrounds, while the paralogous gene, <i>Ksr1</i>, was dispensable for bone homeostasis. Mechanistically, KSR2 regulates bone formation by influencing adipocyte differentiation at the expense of osteoblasts in the bone marrow. Compared with <i>Ksr2</i>'s known role as a regulator of feeding by its function in the hypothalamus, pair-feeding and osteoblast-specific conditional deletion of <i>Ksr2</i> reveals that <i>Ksr2</i> can regulate bone formation autonomously. Despite the gains in appendicular bone mass observed in the absence of <i>Ksr2</i>, bone strength, as well as fracture healing response, remains compromised in these mice. This study highlights the interrelationship between adiposity and bone health and provides mechanistic insights into how <i>Ksr2</i>, an adiposity and diabetic gene, regulates bone metabolism.

Osteogenically differentiated mesenchymal stem cells promote the apoptosis of human umbilical vein endothelial cells in vitro

The absence of blood vessels in tissue engineered bone often leads to necrosis of internal cells after implantation, ultimately affecting the process of bone repair. Herein, mesenchymal stem cells (MSCs) and human umbilical vein endothelial cells (HUVECs) were cocultured to induce osteogenesis and angiogenesis. Based on the findings, the number of HUVECs in the coculture system increased in the growth medium group, but decreased in the osteogenic induction medium (OIM) group. Considering that the paracrine effects of MSCs had changed, we tested the genes expression of osteogenically differentiated MSCs. The expression of osteogenic genes in MSCs increased during osteogenesis. Further, the expression levels of pigment epithelial-derived factor (PEDF) gene and protein, an antivascular factor, were also increased. To verify whether MSCs promote HUVECs apoptosis via PEDF, PEDF was silenced via siRNA. The conditioned medium of differentiated MSCs with PEDF silencing significantly improved the proliferation and apoptosis of HUVECs. Based on further experiments, PEDF mediated the apoptosis and proliferation of HUVECs through p53, BAX/BCL-2, FAS, and c-Caspase-3. However, when PEDF was silenced with siRNA, the osteogenic potential of MSCs was affected. The results of this study provide a theoretical basis for the construction of prevascularized bone tissues in vitro.

Regulation of the integrin αVβ3- actin filaments axis in early osteogenesis of human fibroblasts under cyclic tensile stress

Background

Integrins play a prominent role in osteogenic differentiation by transmitting both mechanical and chemical signals. Integrin expression is closely associated with tensile stress, which has a positive effect on osteogenic differentiation. We investigated the relationship between integrin αVβ3 and tensile stress.

Methods

Human fibroblasts were treated with c (RGDyk) and lentivirus transduction to inhibit function of integrin αVβ3. Y-15, cytochalasin D and verteporfin were used to inhibit phosphorylation of FAK, polymerization of microfilament and function of nuclear YAP, respectively. Fibroblasts were exposed to a cyclic tensile stress of 10% at 0.5 Hz, once a day for 2 h each application. Fibroblasts were harvested on day 4 and 7 post-treatment. The expression of ALP, RUNX2, integrin αVβ3, β-actin, talin-1, FAK, vinculin, and nuclear YAP was detected by Western blot or qRT-PCR. The expression and distribution of integrin αVβ3, vinculin, microfilament and nuclear YAP.

Results

Cyclic tensile stress was found to promote expression of ALP and RUNX2. Inhibition of integrin αVβ3 activation downregulated the rearrangement of microfilament and the expression of ALP, RUNX2 and nuclear YAP. When the polymerization of microfilament was inhibited the expression of ALP, RUNX2 and nuclear YAP were decreased. The phosphorylation of FAK induced by cyclic tensile stress reduced by the inhibition of integrin αVβ3. The expression of ALP and RUNX2 was decreased by inhibition of phosphorylation of FAK and inhibition of nuclear YAP.

Conclusions

Cyclic tensile stress promotes osteogenesis of human fibroblasts via integrin αVβ3-microfilament axis. Phosphorylation of FAK and nuclear YAP participates in this process.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02597-y.

Parallels between the extracellular matrix roles in developmental biology and cancer biology

Interaction of a tumor with its microenvironment is an emerging field of investigation, and the crosstalk between cancer cells and the extracellular matrix is of particular interest, since cancer patients with abundant and stiff extracellular matrices display a poorer prognosis. At the post-juvenile stage, the extracellular matrix plays predominantly a structural role by providing support to cells and tissues; however, during development, matrix proteins exert a plethora of diverse signals to guide the movement and determine the fate of pluripotent cells. Taking a closer look at the communication between the extracellular matrix and cells of a developing body may bring new insights into cancer biology and identify cancer weaknesses. This review discusses parallels between the extracellular matrix roles during development and tumor growth.